Dampened choke coil

ABSTRACT

A damped electrical coil structure wherein either the coil and its ferromagnetic core or an associated resistor is formed in the shape of a tube and the other of the two elements is placed at the interior of the tube. The resistor and the coil are connected in parallel relationship by an electrically conductive compound which bridges the gap formed by the walls of the tube and the electrical element placed at the interior thereof.

United States Patent 1191 Kaiserswerth et al.

[ DAMPENED CHOKE COIL [7 5 Inventors: Hans-Peter Kaiserswerth,

Regensburg; Josef Wimmer, Wenzenbach; Rudolf Schaller, Regensburg, all of Germany [73] Assignee: Siemens Alrtiengesellschaft, Berlin and Munich, Germany [22] Filed: Mar. 9, 1973 [21] Appl. No.: 339,736

[30] Foreign Application Priority Data Mar. 17, 1972 Germany 7210297[U] Mar. 17, 1972 Germany 7210330[U] [52] US. Cl. 323/78, 336/83 [51] Int. Cl G05f 3/02, HOlf 17/06 [58] Field of Search 1336/83, 96, 221, 84, 222, 336/223, 105, 192;323/74, 76, 78; 333/79, 70 S, 70 CR; 338/211, 212

[56] References Cited UNITED STATES PATENTS 1,031,043 10/1933 Taylor 333/70 s 1451 Sept. 10, 1974 2,368,474 1/1945 Keister 333/70 S 2,692,372 10/1954 Goldstin 336/222 X 2,976,502 3/1961 Hill 336/83 3,171,091 2/1965 Goldsmith 336/83 3,176,217 3/1965 Matsushima et a1 336/105 3,295,055 12/1966 Matsushima et al 336/83 X Primary Examiner-Thomas J. Kozma Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [57] ABSTRACT 1 Claim, 3 Drawing Figures PATENIE SEP 1 01974 SHEET 1 [W 2 Fig.1

' Fig.2

Z/kQ

f/MHz 1 DAMPENED CHOKE COIL BACKGROUND OF THE INVENTION Field of the Invention The field of art to which this invention pertains is a damped coil structure in which either the coil or the resistor is formed as a tube with the other of the two elements being positioned at the interior of the tube. The coil and the resistor are connected in parallel to form a damped circuit.

SUMMARY OF THE INVENTION It is an important feature of the present invention to provide an improved damped electrical coil structure.

It is another feature of the present invention to provide a damped electrical coil structure wherein either the coil or the damping resistor is formed in the shape of a tube.

It is a further object of the present invention to provide a damped coil structure described above wherein one of the two members forming the damped coil structure is placed interiorly of the other member.

It is an object of the present invention to provide a coil structure wherein the coil is formed on a tube and a resistor is connected in parallel with the coil and positioned interiorly of the tube.

It is also an object of the present invention to provide a coil structure wherein a resistor is formed in the shape of a tube and a coil structure is wound interiorly of the tube with the two electrical elements being connected in parallel relation.

These and other objects, features and advantages of the present invention will be understood in greater detail from the following description and theassociated drawings wherein reference numerals are-utilized to designate a preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a coil structure according to the present invention wherein the resistor is formed in theshape of a tube and an electrical coil is positioned at the interior of the tube. r

FIG. 2 is a graph showing the effect of using a damping resistor on a coil such as that shown in FIG. 1.

FIG. 3 is a coil structure also according to the present invention wherein the coil is wound in the form of a tube and a resistor is placed interiorly of the tube and both elements are connected in parallel relation.

DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention relates to a damped electrical coil which has a ferromagnetic core and a winding of wire. Such coils are often used for a wide variety of frequency ranges. It cannot always be assured that the coil will not form a resonance circuit with capacitances which are in the circuit such as parasitic capacitances and the like. The result of such a resonant circuit, of course, is current or voltage elevation in an undesirable manner. These undesirable effects, however, do not occur if the Q of the circuit is sufficiently low namely, less than I.

In order to achieve this result, a resistor may be connected in parallel with the choke coil which has a value such as the equivalent of the impedance of the coil at the resonant frequency. In most cases, such resistors are undesirable because they are additional components which must be installed and which add to the cost of the unit. Not only is high cost a factor, but insulation of a resistor of this type also utilizes additional space in the assembly.

It is already known to apply the winding of a coil directly on a cylindrical resistor, for instance, on a carbon layer resistor. Such an arrangement, however, has very little self-induction so that a choke effect can only be achieved at a very high frequency. There is also known a high frequency choke coil with a ferrite core characteristic if they are not particularly intended for high frequency operation.

The present invention accomplishes the desired task of finding a damped choke coil which has all the desirable characteristics but which does not have the damaging effects of resonance magnification.

This is accomplished in the present invention by providing a choke winding which is in parallel with an electrical resistor wherein the resistor or the core of the coil are hollow so that the other element is placed interiorly of the hollow element. The ends of the resistor are then connected respectively with the ends of the choke winding to form the parallel electrical relationship.

By one method, the ferromagnetic core is designed as a tube and the resistance is positioned at the interior of the tube. The tube 4 can consist of a ferrite material, carbonyl iron or of suitable sheet metal. It is desirable that in such an arrangement the value of resistance be independent of the frequency of operation. Preferably in the hollow space of the tube core, a symmetrical wire or layer resistor may be arranged, and if necessary, attached by a suitable cement. The connecting wires of the resistor form junctions with the connecting wires of the coil.

Another form of the invention shows the resistor in the form of a tube and the choke winding is positioned interiorly of the tube. The tube serving as a resistor can consist of ceramic, glass or a ferromagnetic material. It may be provided either inside or outside with a resistance layer. If the resistance layer is provided interiorly on the tube, the unit is left electrically insulated at the outside. The resistor can be a wire resistor or a layer re sistor or a lump type resistor.

Contacting between the ends of the choke winding and the resistor may take place by soldering if both have wire connections or by an electrically conductive glue to bridge the gap between the tube walls and the interior element. In addition, the coil may be shielded by a magnetic material and the entire unit may be filled with a compound. By this step, the magnetic field and the self-induction can be increased. Finally, such components are desirably insulated with regard to the outside of the unit, for instance, by covering with a hose of insulating material.

Referring to the drawings in greater detail, FIG. 1 shows a sectional view of a coil according to the invention. In FIG. 1, the core 1 is formed of a magnetic material and on the outer side thereof a winding 2 of copper wire is formed. The ends 7 of the winding 2 are soldered with the outer connecting parts 3. A tube core 4 of insulating material is caused to surround the choke coil, and the tube core is provided with a resistance on the inner surface thereof. The resistance is identified by numeral 5. The electrical connection between the resistance and the connecting wire 3 in FIG. 1 takes place by means of an electrically conductive glue 6 which also closes off the inner space of the tube. The carrier member 4 and the resistance layer 5 thereby form the electrical resistor identified by the numeral 8.

FIG. 2 shows a logarithmic illustration of the dependency of the alternating current resistance Z of the structure according to FIG. 1 on the frequency f. The winding has an inductivity of-L p.ul-I. The resistance layer has a resistance value of R 800 ohms. To achieve these curves, the device was measured with an additionalcapacitor having a capacity of IOpF which was connected in series with the unit in order to simulate scattered capacity in a typical circuit.

The curve (a) shows the results without a resistor. Definite resonance points A and self resonance B are recognized. The curve (b) shows the results with the resistor added as shown in FIG. 1. It is noticed that the definite resonance points disappeared. In particular, the series resonance A strongly decreases.

' FIG. 3 shows another embodiment of the present invention. In FIG. 3a tube core 1 consisting of a magdevelop high frequencies.

We claim:

1. The combination of an electrical coil having connection wires at opposite end thereof, an associated ferromagnetic core, the connection wires of the coil being firmly anchored to opposite ends of the ferromagnetic core and extending outwardly therefrom, a cylindrical'member having the coil and core contained inside thereof, a resistance layer positioned on the in side surface of the cylindrical member, an electrically conductive glue making electrical connection between the resistance member and the connection wires at opposite ends of the cylindrical member, and said electrically conductive glue also sealing off the interior of the cylindrical member from the exterior thereof. 

1. The combination of an electrical coil having connection wires at opposite end thereof, an associated ferromagnetic core, the connection wires of the coil being firmly anchored to opposite ends of the ferromagnetic core and extending outwardly therefrom, a cylindrical member having the coil and core contained inside thereof, a resistance layer positioned on the inside surface of the cylindrical member, an electrically conductive glue making electrical connection between the resistance member and the connection wires at opposite ends of the cylindrical member, and said electrically conductive glue also sealing off the interior of the cylindrical member from the exterior thereof. 